The disclosure relates generally to a low temperature cofired ceramic structure and a method of making such structure.
Precision pneumatic suppressors are commonly used in for example medical devices and systems to generate accurate pressure drop over the predetermined precision suppressor. The pressure drop generated by the suppressor may be used for protecting a pressure sensitive device such as pressure sensor. Furthermore the magnitude of the pressure drop can be measured with a differential pressure measurement connected over the suppressor and that pressure information can be further used to determine the fluid flow rate through the channel. Moreover precision suppressors can be used to adjust accurate fluid flow rates and flow ratios between two or more channels that form a net of channels, which connect together at one point. Fluid flow rate though each channel is adjusted by the absolute constriction of that specific channel together with the constriction ratio of precision suppressors in respect to constrictions in other channels. Another form of application is to connect suppressors to volumes to form pneumatic filters to filter alternating pressures and noise in the system etc. The frequency band of such filter can be adjusted with the magnitude of suppression and the size of the volume.
Conventional precision stainless steel tubes are commonly used to generate accurate pneumatic constrictions. Manufacturing tolerances of such precision stainless steel tubes are rather high and the constriction they produce may deviate more than 25% from its nominal value. Some devices are extremely sensitive for such tolerances. Of course by measuring the value of constriction of each suppressor, then sorting and selecting pieces that are within the manufacturing specification, can increase the manufacturing yield of produced devices. On the contrary this kind of manufacturing process is time consuming, uneconomical and first of all very expensive. Precision stainless steel tubes are usually connected to tubing or similar by hand. They can also be placed inside a plastic mould including some larger cavities as well as input and output ports outside the mould to connect suppressors to a device or a system. As suppressors need to be connected to tubing or a plastic mould the device size is increased considerably making it clumsy. Each connection between the tubing and, or plastic mould also causes a risk of leakage.
Low Temperature Co-fired Ceramics (LTCC) is a well-established process that has been in use for many years in the microelectronics packaging industry. It is similar to the thick film hybrid process employed for multilayer ceramic capacitors and chip inductors. LTCC technology is especially used for wireless and high-frequency applications. In RF and wireless applications, LTCC technology is also used to make multiplayer hybrid integrated circuits, which can include resistors, inductors, capacitors, and active components in the same package. In general LTCC hybrids have a smaller initial cost as compared with for example ICs, making them an attractive alternative for small-scale integration devices. It is also known to use said LTCC process to make elements having micro-channels and cavities for fluids. These known solutions are however only designed for through flow of a medium, i.e. having no intention to create pneumatic constrictions.